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<h1 id="performance-tuning">Performance tuning</h1>
<div class="admonition attention">
<p class="admonition-title">Attention</p>
<p>Check out the lightweight on-premises email archiving software developed by iRedMail team: <a href="https://spiderd.io/">Spider Email Archiver</a>.</p>
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<div class="toc">
<ul>
<li><a href="#performance-tuning">Performance tuning</a><ul>
<li><a href="#setup-a-dns-server-in-lan-or-localhost-to-cache-dns-queries">Setup a DNS server in LAN or localhost to cache DNS queries</a></li>
<li><a href="#enable-postscreen-service-to-help-reduce-spam">Enable postscreen service to help reduce spam</a></li>
<li><a href="#update-amavisd-postfix-config-files-to-process-more-emails-concurrently">Update Amavisd + Postfix config files to process more emails concurrently</a></li>
</ul>
</li>
</ul>
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<p>If you're running a busy mail server (many inbound/outbound emails every day),
you can follow below suggestions for better performance.</p>
<h3 id="setup-a-dns-server-in-lan-or-localhost-to-cache-dns-queries">Setup a DNS server in LAN or localhost to cache DNS queries</h3>
<p>Mail services <strong>heavily</strong> rely on DNS service and perform many many DNS queries,
a cache DNS server in LAN or localhost helps <strong>A LOT</strong>:</p>
<ul>
<li>It speeds up DNS queries. This helps a lot to speed up mail flow.</li>
<li>It reduces DNS queries to DNSBL servers, so that you can continue using their
  excellent service without exceeding the max query limit.</li>
</ul>
<h3 id="enable-postscreen-service-to-help-reduce-spam">Enable postscreen service to help reduce spam</h3>
<ul>
<li><a href="./enable.postscreen.html">Enable postscreen service</a></li>
</ul>
<p>If you don't want to use postscreen service, you can <a href="./enable.dnsbl.html">enable DNSBL service</a>
instead, it helps a lot too. Although both <code>postscreen</code> and pure DNSBL services
uses the same DNSBL servers, but <code>postscreen</code> offers additional solutions to
reduce spam, so postscreen is better.</p>
<p>postscreen and DNSBL service help catch a lot spam before putting the spams
in local mail queue, so they save much system resource.</p>
<h3 id="update-amavisd-postfix-config-files-to-process-more-emails-concurrently">Update Amavisd + Postfix config files to process more emails concurrently</h3>
<ul>
<li><a href="./concurrent.processing.html">Process more emails concurrently</a></li>
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